1. Technical Field
The invention relates to the determination of the physical linear position of an object that in itself is located in a harsh environment, and more particularly, includes systems required in the field of nuclear power generators.
2. Background Art
There are many position sensors and range detectors that are commercially available. Some of these are known to use the measuring technique of linear resistive sensing. However, these known measuring schemes and devices cannot operate in the harsh environments, such as high temperature, high pressure, or various fluid environments, which this invention can. Moreover, no such position sensors are known to operate continuously within the core of a nuclear reactor.
The present invention is a high resolution, high reliability, magnetically coupled, linear position sensor that provides a means of determining the position of an object using a methodology that does not require a hard mechanical or physical connection between the sensor and the object whose position is to be determined. The present invention can operate in harsh environments such as those having high temperature (650° F., 343° C.), high pressure (2500 psia, 172 Bars, 17236893 Pa), or various fluid (air, water, oil, etc.) with exposure to moderate levels and types of radioactivity, including those characteristic of a nuclear power plant core having neutron flux, gamma ray, heat, and other radiations. The sensor utilizes dual rod elements with a magnetically coupled bridging contact “slider” supported by a ceramic guide all of which are contained within a non magnetic pressure housing. The topology of the sensor supports at least two types of measurement techniques, Time Domain Reflectometry (TDR) as well as linear resistive to determine target position.
Although the nature of each component of the sensor is simple as considered individually, the collective application of the rod elements, spherical shaped slider, and the ceramic guide are a novel approach to provide a high resolution, high reliability sensor. Moreover, all of the materials used to fabricate the components as described herein are selected to satisfy the temperature operating range, which may be a nontrivial determination.
The inserted position of a control rod assembly used in a nuclear reactor core must be determined with high accuracy. Additionally, incremental linear motions of the control rod assembly must be determined so that the need for a measuring sensor with high resolution is necessary. This capability allows the most efficient management of nuclear control rod consumption promoting a high efficiency. It is also a redundant means of verifying a SCRAM function. All existing reactor plant control rod sensors are strictly used outside of the reactor core through extensions of the control rod into an integrated standpipe within the reactor head. To minimize complexity, this sensor will operate within the reactor core, utilizing only a small penetration for wiring.
The result of this or similar applications is that the position sensor will see a very harsh environment. It can be immersed in water (the reactor coolant media). The pressures can be as high as 2500 psig (17236893 Pa, 172 Bars). The temperature will range from −32° F. (−36° C.) to a maximum of 650° F. (343° C.), additionally the sensor will be exposed to radiation.
The linear position sensor of the present invention solves all of these problems and is adaptable to the other applications mentioned herein.
While the above references introduce and disclose a number of noteworthy advances and technological improvements within the art, none completely fulfills the specific objectives achieved by this invention.